Multiple antenna elements may be used together to form an array antenna. The array antenna radiation pattern can be derived from the location information and the radiation patterns of the individual antenna elements. The array antenna has evolved from a linear array in which elements are aligned in a straight line, to a planar array in which elements are placed in a plane, to conformal arrays in which elements are placed on a non-planar surface such as the skin of an airplane, to distributed arrays in which elements are randomly distributed over a relatively wide range and each element may also have transmitting and receiving capabilities.
The distributed array has great advantages for the interconnection of energy-limited and massively distributed devices, such as an unattended ground sensors (UGS) network. The UGS are typically deployed at a distance, remote from the users who are receiving the sensor information. Communication between an external command station and the UGS can be accomplished with a satellite link. However, a satellite link is expensive both in power and size. However, using the UGS to transmit and receive in the fashion of a distributed array antenna can increase the distance between an external command station and the UGS network without the penalties of power consumption and size that a satellite communication link imposes. However, typical approaches for forming a virtual distributed array using the UGS nodes do not account for the information exchange growth due to representing data digitally, the local bandwidth limitations, and the energy impact on battery operated nodes.
For example, in a typical approach, each node receives a signal from the remote command station and then retransmits a digital representation of the received spread spectrum signal to the local central unit. This approach suffers from information exchange growth. In particular, the number of bits needed for the re-transmitted signal per bit of actual message is typically b=C×S×B×2, where C is the number of chips per bit, S is the digital sample rate, and B is the number of digital bits required to maintain sufficient dynamic range. The factor of two is required to send both I and Q. Typical values of C, S, and B are 128 chips/bit, 4 samples/chip, and 16 bits/sample, respectively. If each node transmits a signal of this length, the inflation rate (IR) is
            I      R        =          2      ×      C      ×      S      ×      B      ×      M      ×                        R          R                          R          L                      ,where M is the total number of nodes, RR is the data rate of the remote channel (i.e. the channel between the remote transmitter and the nodes) and RL is the data rate of the local digital channel (i.e. the channel between the nodes and a central unit). The factor M is included because the nodes transmit one at a time so as not to interfere with each other. Assuming the typical values mentioned above, and a local data rate 10 times faster than the remote data rate, the inflation rate is 1638.4×M . In other words, if the original message length is one second and 10 nodes are used, the time to receive the message is greater than 4 hours! This is not only an impractical time limitation, it also greatly reduces battery life since the longer the nodes are receiving and transmitting, the more battery is used up.
Therefore, for the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a distributed array antenna which reduces the inflation rate of time to receive a message without a substantial increase in the power requirement.